The signal was lost one minute before the plane entered Vietnam's air jurisdiction on its way to Beijing, the army said.

KUALA LUMPUR, MALAYSIA - MARCH 08: Datuk Hishamuddin Hussein, Minister of Transport speaks to the media at the Kuala Lumpur International Airport on March 8, 2014 in Kuala Lumpur, Malaysia. Malaysia Airlines Flight MH370 from Kuala Lumpur to Beijing carrying 239 onboard was reported missing after the crew failed to check in as scheduled while flying over the sea between Malaysia and Ho Chi Minh City in Vietnam, according to published reports. (Photo by How Foo Yeen/Getty Images)How Foo Yeen / Getty Images